Pik is a tool to manage multiple versions of ruby on Windows. It can be used from the Windows command line (cmd.exe), Windows PowerShell, or Git Bash. I have yet to test on cygwin.
>pik help commands
add Adds another ruby location to pik.
benchmark|bench Runs bencmarks with all versions that pik is aware of.
checkup|cu Checks your environment for current Ruby best practices.
config Adds/modifies configuration options.
default Switches back to the default settings.
gem Runs the gem command with all versions that pik is aware of.
gemsync Synchronizes gems from the version specified to the current version.
help Displays help information.
implode Removes your pik configuration.
info Displays information about the current ruby version.
install|in Downloads and installs different ruby versions.
list|ls Lists ruby versions that pik is aware of.
rake Runs the rake command with all versions that pik is aware of.
remove|rm Removes a ruby location from pik.
ruby|rb Runs ruby with all versions that pik is aware of.
run Runs command with all versions of ruby that pik is aware of.
switch|sw|use Switches ruby versions based on patterns.
tag Adds the given tag to the current version.
tags Runs the pik command against the given tags.
uninstall|unin Deletes a ruby version from the filesystem and removes it from Pik.
update|up updates pik.
For help on a particular command, use 'pik help COMMAND'.